The present invention is directed to a gas lens collet body and more specifically to a gas lens collet body used in the gas tungsten arc welding (GTAW) process.
Inert gas shielded welding torches have been in common use for many years. These torches employ a fixed tungsten metal electrode contained within a torch head constructed so that the electrode and welding zone is surrounded by a blanket of an inert gas. The gasses most normally used are helium and argon. Welding torches of this type are used especially with metals that are highly sensitive to oxidation. For many years, the industry standard gas lens collet body was constructed of two pieces. A first piece was the collet body stem made of copper and the second piece was an outer body shell made of brass. The copper collet body stem and the brass outer body shell were brazed together. The gas lens was provided with a central axially extending passage which tapered down at one end to a smaller diameter passage for receiving an electrode. An outer annular passage surrounded the inner passage and a plurality of radially extending bores were provided for directing the flow of a shield gas from the inner axially extending passage to the outer annular passage. A plurality of fine mesh screens were mounted at the forward end of the collet body stem in the annular passage for providing a non-turbulent flow of gas around the weld area.
Due to the use of the brass and the two-piece construction of the gas lens collet body, the lower conductivity and higher resistance of the brass causes the gas lens collet body to heat up more rapidly. The rapid heating would lead to substantial thermal expansion causing cracking of alumina oxide nozzles which were mounted on the body. Furthermore, the different co-efficients of thermal expansion between the copper collet body stem and the brass outer body shell would cause uneven expansion leading to the failure of the brazed joint therebetween, thereby causing a shielding gas leak. The provision of the radially directed holes interconnecting the axial passage and the annular passage causes a substantial increase in pressure leading to undue turbulence in the annular passage which could not be completely eliminated by the gas lens.
The U.S. patent to Kleppen (U.S. Pat. No. 4,788,401) discloses an inert gas welding torch and discloses the radial arrangement of the holes between an axial passage and an annular passage through which the shield gas will pass to the gas lens with the same drawback as noted above.